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# mfft

multi-dimensional fft

### Calling Sequence

`[xk]=mfft(x,flag,dim)`

### Arguments

x

`x(i,j,k,...)` input signal in the form of a row vector whose values are arranged so that the i index runs the quickest, followed by the j index, etc.

flag

(-1) FFT or (1) inverse FFT

dim

dimension vector which gives the number of values of `x` for each of its indices

xk

output of multidimensional fft in same format as for `x`

### Description

FFT for a multi-dimensional signal

For example for a three dimensional vector which has three points along its first dimension, two points along its second dimension and three points along its third dimension the row vector is arranged as follows

```x=[x(1,1,1),x(2,1,1),x(3,1,1),...
x(1,2,1),x(2,2,1),x(3,2,1),...
x(1,1,2),x(2,1,2),x(3,1,2),...
x(1,2,2),x(2,2,2),x(3,2,2),...
x(1,1,3),x(2,1,3),x(3,1,3),...
x(1,2,3),x(2,2,3),x(3,2,3)]```

and the `dim` vector is: `dim=[3,2,3]`

`mfft` is superseeded by fft: `mfft(x,flag,dim)` is equivalent to `matrix(fft(matrix(x,dim),flag),size(x))`.